Energy storage is a crucial component of a large number and variety of electronic devices, particularly mobile devices and vehicles, such as electric and hybrid gas-electric vehicles (also “hybrid vehicles” herein). Energy storage devices can be based on a variety of physical effects. For example, electric fields can be employed to store energy in capacitors, and chemical reactions (involving ion motion) can be employed to store energy in batteries. However, energy storage in a capacitor can be limited by the geometry of current devices (e.g., 2-D capacitor plates having limited surface areas) and either a low permittivity or low dielectric breakdown voltage, and batteries can have a slow response time due to the relatively slow ion motion inherent in electrochemical reactions.
There are limitations associated with current batteries. For example, current batteries can have low storage densities due to the relatively low voltage (<5V) resulting from the electrochemical reactions of the ions. In addition, the low mobility of ions in current batteries can lead to slow charge and discharge performance. Furthermore, the reliance of existing batteries on ionic transport causes high degradation rates of the batteries. The performance of battery powered devices, such as hybrid or electric vehicles, can be limited by the low energy stored per weight of batteries used in such vehicles.
An important characteristic of a dielectric material is its dielectric permittivity. Different types of dielectric materials are used for capacitors and include ceramics, polymer film, paper, and electrolytic capacitors of different kinds. The most widely used polymer film materials are polypropylene and polyester. Increasing dielectric permittivity allows for increasing volumetric energy density, which makes it an important technical task.
Second-order nonlinear optical (NLO) effects of organic molecules have been extensively investigated for their advantages over inorganic crystals. Properties studied, for example, include their large optical non-linearity, ultra-fast response speed, high damage thresholds and low absorption loss, etc. Particularly, organic thin films with excellent optical properties have tremendous potential in integrated optics such as optical switching, data manipulation and information processing. Among organic NLO molecules, azo-dye chromophores have been a special interest to many investigators because of their relatively large molecular hyper-polarizability (b) due to delocalization of the p-electronic clouds. They were most frequently either incorporated as a guest in the polymeric matrix (guest-host polymers) or grafted into the polymeric matrix (functionalized polymers) over the past decade.
Hyper-electronic polarization of organic compounds is described in greater detail in Roger D. Hartman and Herbert A. Pohl, “Hyper-electronic Polarization in Macromolecular Solids”, Journal of Polymer Science: Part A-1 Vol. 6, pp. 1135-1152 (1968). Hyper-electronic polarization may be viewed as the electrical polarization external fields due to the pliant interaction with the charge pairs of excitons, in which the charges are molecularly separated and range over molecularly limited domains. In this article four polyacene quinone radical polymers were investigated. These polymers at 100 Hz had dielectric constants of 1800-2400, decreasing to about 58-100 at 100,000 Hz. Essential drawback of the described method of production of material is use of a high pressure (up to 20 kbars) for forming the samples intended for measurement of dielectric constants.
Copolymers of methyl methacrylate with a methacrylate containing a rigid group with two azo bonds (3RM) were prepared and their photoinduced birefringence levels and rates studied in X. Meng, A. Natansohn and P. Rochon, “Azo polymers for reversible optical storage: 13. Photoorientation of rigid side groups containing two azo bonds”, Polymer Vol. 38 No. 11, pp. 2677-2682, (1997). Birefringence levels of 0.11 for the copolymer with 11.6 mol % azo structural units and 0.13 for the copolymer with 30.0 mol % azo structural units were found; this is higher than the birefringence inducible in a typical azo homopolymer containing a chromophore with only one azo group, poly{4′-[(2-(acryloyloxy) ethyl)ethylamino]-4-nitroazobenzene} [poly(DR1A)]. The birefringence per azo structural unit for a copolymer containing 11.6 mol % 3RM is about five times that for a DR1A copolymer with similar azo content, because of the intrinsic structural properties of 3RM (high length/diameter ratio). Dichroism in both u.v. and visible regions of the spectrum contribute to the overall photoinduced birefringence. The rate of inducing birefringence in the 3RM copolymers is lower than in poly(DR1A) and the birefringence stability (91-96% of the induced birefringence is maintained after the writing laser is off) is much better than that for poly(DR1A) (about 80%). The good stability and slow birefringence growth rate are due to the lesser mobility of the larger side group. Novel polymers with azobenzene moiety with alkyl spacer and different substituents units are presented in VitaliySmokal, Oksana Krupka, Agnesa Sinugina, and Vladimir Syromyatnikov, “Synthesis, Characterization, and Study of Novel Push-Pull Azobenzene Polymers”, Mol. Cryst. Liq. Cryst., Vol. 590: pp. 105-110, (2014). Azopolymers were obtained by a two-step synthetic approach. This includes the preparation of a methacrylic monomers and their polymerization. Their photophysical and photochemical properties have been investigated. Polymers were characterized and evaluated by 1HNMR, IR, UV spectroscopy. Thermal stability was characterized by DSC method. The synthesized polymers exhibited glasstransition temperatures in the range of 110-140° C.
The second- and third-order nonlinear optical response of spin-deposited thin films of three different push-pull side chain azobenzene polymers is investigated by the second- and third-harmonic Maker fringes techniques using 30 ps laser pulses at a fundamental wavelength of 1064 nm in Hasnaa El Ouazzani et. al., “Second- and Third-Order Nonlinearities of Novel Push-Pull Azobenzene Polymers”, J. Phys. Chem. B, vol. 115, pp. 1944-1949 (2011). Measurements were carried out before and after aligning the chromophores by corona poling of the films, while different polarization configurations have been utilized. Strong dependence of the response upon the structure of the systems has been found, which is related to the different charge transfer within the molecules. The reported findings are compared with already published results.
The synthesis of side chain methacrylic polymers functionalized with azobenzene chromophores is described in greater detail in Oksana Krupka et. al., “ELECTRO-OPTICAL PROPERTIES IN THIN FILMS OF NEW AZOBENZENE POLYMERS”, CHEMISTRY & CHEMICAL TECHNOLOGY, Vol. 9, No. 2, pp. 137-141, (2015). A reversible change of thin film absorption is observed when illuminating it with monochromatic, linearly polarized light under the applied external DC field. The amount of change depends on the angle between the light polarization and the DC electric field direction.
It is known that energy storage device based on capacitor have well-known advantages versus with electrochemical energy storage device, e.g. a battery. However, an ordinary energy storage device based on capacitor often do not store energy in small volume or weight as in case of a battery, or at low energy storage cost, which makes capacitors impractical for some applications, for example electric vehicles. Compared to batteries, disclosed solid state energy storage device is able to store energy with very high power density, i.e. charge/recharge rates, have long shelf life with little degradation, and can be charged and discharged (cycled) hundreds of thousands or millions of times.